This invention relates generally to heat exchanger coils and, more particularly, to a method and apparatus for the assembly of plate fin heat exchanger coils.
A plate fin heat exchanger coil is commonly constructed with a plurality of flat, parallel plates having laterally spaced holes therein for receiving refrigerant tubes, or hairpin tubes, therein. At each end of the plate fin bundle, there is a tube sheet composed of heavier material, and adjacent the upper tube sheet, the open ends of the hairpin tubes are fluidly connected by way of U-shaped return bends that are secured thereto by way of brazing or the like. When the coils are installed into a refrigeration system, the refrigerant is made to flow through the hairpin tubes, and the air to be cooled or heated is made to flow over the plate fins, such that a heat transfer is thereby affected.
In the assembly of plate fin heat exchangers, it is known to receive the individual plate fins from the plate fin harvester and to stack them on a rod assembly for subsequent transfer, as a bundle, to the plurality of hairpin tubes. Traditionally, much of this process has been accomplished manually by an operator. This can be tedious and time consuming when considering the successive requirements of: accumulating the exact number of plate fins in a bundle; maintaining the proper orientation of the plate fins while moving them into registration with the hairpin tubes; maintaining the exact number of hairpin tubes in the proper arrangement and orientation for registration with the plate fins; and lacing each of the hairpin tubes into the fin bundle to form the coil structure. In this regard, it should be understood that the holes formed in the plate fins are only very slightly larger than the hairpin tubes in order to minimize the subsequent required expansion of the tubes into a tight fit, heat exchanging relationship with the plate fins. Accordingly, the control of the relative positions of the plate fins and the hairpin tubes during assembly is very critical.
One approach that has been used with some success is that of feeding the plate fins into one end of a chute which closely surrounds the edges of the plate fins to thereby precisely maintain their orientation, such that when they emerge at the other end of the chute they can have the precisely positioned hairpin tubes laced into them. However, such an approach has been found to be impractical where the plate fins are very thin and not likely to remain on edge during movement through the chute.
It is therefore an object of the present invention to provide an improved method and apparatus for the assembly of a plate fin heat exchanger.
Another object of the present invention is the provision for an improved method and apparatus for accumulating, orienting, and transferring an exact number of plate fins to a position where they can be assembled onto a plurality of hairpin tubes.
Yet another object of the present invention is the provision for an improved method and apparatus for automatically lacing a plurality of hairpin tubes into a fin bundle.
Still another object of the present invention is the provision for an automatic plate fin lacing method and apparatus which is economical and practical in use.
These objects and other features and advantages become more readily apparent upon reference to the following description when taken in conjunction with the appended drawings.